Light emitting diodes (LEDs) are semiconductor light emitters that can emit light in one or various colors, such as ultraviolet, blue, green, yellow or red. LEDs have been improved to a point with respect to operating efficiency such that LEDs are now replacing conventional light sources in traditional lighting applications, such as backlighting for LCD displays, traffic signal lights, automotive taillights and electronic flashes. This is due in part to the fact that LEDs have many advantages over conventional light sources. These advantages include longer operating life, lower power consumption, and smaller size.
In some devices, one or more photodetectors are used with LEDs to sense incident light, which may be from an external source or the LEDs. As an example, a camera cell phone includes one or more LEDs and a photodetector. The LEDs are used to produce a flash of light when taking a picture under low light conditions. The LEDs require a circuit to provide driving signals to the LEDs in order to activate the LEDs. The LEDs also typically require optics to focus the light emitted from the LEDs. The photodetector is used to detect ambient light conditions so that the light function of the camera cell phone can be set to an appropriate setting, e.g., the LEDs can be set to either “ON” or “OFF” mode. The photodetector requires its own circuit to measure the amount of current generated by the photodetector in response to incident light. Similar to the LEDs, the photodetector also typically requires optics to focus the incident light onto the photodetector.
A concern with the conventional system of LEDs and photodetector is that the associated optics and circuits to operate the LEDs and the photodetector require a significant amount of space in the camera cell phone. This requirement hinders the development of more compact camera cell phones. The associated optics and circuits also add to weight and manufacturing cost of the camera cell phone.
Another concern with the conventional system of LEDs and photodetector is that the photodetector requires an additional opening on the same side of the camera cell phone as the LEDs, which tends to cause aesthetic and styling issues to camera cell phone designers.
In view of these concerns, what is needed is a system and method for emitting and detecting light that requires less circuitry and optics, and eliminates the need for an additional opening in the camera cell phone.